diff --git a/ChangeLog b/ChangeLog
index 67dd495b37..5c69ace214 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,18 @@
+Thu Nov 27 15:59:16 2008  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* gc.c (ruby_stack_check): no check if using sigaltstack.
+
+	* signal.c (ALT_STACK_SIZE): default minimum size is insufficient
+	  for method calls.
+
+	* signal.c (sigsegv): handles stack overflow if possible.
+
+	* thread.c (ruby_thread_stack_overflow): helper function to raise
+	  sysstack_error.
+
+	* thread_pthread.c (ruby_stack_overflowed_p): checks for stack
+	  overflow.
+
 Thu Nov 27 10:40:52 2008  Yukihiro Matsumoto  <matz@ruby-lang.org>
 
 	* ext/bigdecimal/bigdecimal.c (BigDecimal_div2): should return
diff --git a/signal.c b/signal.c
index df41ddbdfd..e16308eebb 100644
--- a/signal.c
+++ b/signal.c
@@ -417,7 +417,7 @@ typedef RETSIGTYPE (*sighandler_t)(int);
 #ifdef USE_SIGALTSTACK
 #define SIGINFO_ARG , siginfo_t *info, void *ctx
 #ifdef SIGSTKSZ
-#define ALT_STACK_SIZE SIGSTKSZ
+#define ALT_STACK_SIZE (SIGSTKSZ*2)
 #else
 #define ALT_STACK_SIZE (4*1024)
 #endif
@@ -431,7 +431,7 @@ register_sigaltstack()
     if (is_altstack_defined)
       return;
 
-    newSS.ss_sp = malloc(ALT_STACK_SIZE * 2);
+    newSS.ss_sp = malloc(ALT_STACK_SIZE);
     if (newSS.ss_sp == NULL)
       /* should handle error */
        rb_bug("register_sigaltstack. malloc error\n");